Spring and shunt assembly for circuit interrupter

ABSTRACT

The invention relates to a high voltage circuit interrupter construction in which a fusible means is disposed inside a tubular insulating casing or holder and electrically connected in series with an elongated conducting member which is axially movable through a body of arc extinguishing material and is biased upwardly by a coil tension spring which is disposed within a spring guide to prevent overlapping of the turns during movement which might damage the spring and prevent its repetitive use.

United States Patent [1 Cameron et al.

SPRING AND SHUNT ASSEMBLY FOR CIRCUIT INTERRUPTER Inventors: Frank L. Cameron, North Huntingdon; Robert C. Iandola, Langhorne, both of Pa.

Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed: May 15, 1974 Appl. No.: 470,105

Assignee:

US. Cl. 337/178; 337/219; 337/275 Int. Cl. "01h 71/10 Field of Search 337/169, 170, 171-175,

References Cited UNITED STATES PATENTS 9/1942 Williams, Jr 337/276 X 4/1943 Wallace ..l 4. 337/178 I [In 3,886,512 [451 May 27, 1975 3,401,244 9/1968 Patterson 4 337/178 3,447,114 5/1969 Frink ct all 337/171 3,629,768 12/1971 Scherer 337/275 Primary Examiner-J. D. Miller Assistant ExaminerFred E. Bell Attorney, Agent, or Firm-M. .l. Moran [57] ABSTRACT The invention relates to a high voltage circuit interrupter construction in which a fusible means is disposed inside a tubular insulating casing or holder and electrically connected in series with an elongated conducting member which is axially movable through a body of arc extinguishing material and is biased upwardly by a coil tension spring which is disposed within a spring guide to prevent overlapping of the turns during movement which might damage the spring and prevent its repetitive use.

10 Claims, 6 Drawing Figures PATENTEDmzT I915 3.886512 SHEET 1 9. IO I *1") ll, a a '1 --s2 FIG. I

FIG. 2

PATENTEDMAYN ms 3.886512 SHEET 2 FIG. 3.

PATENTEU HAYZ'! I975 SHEET FIG. 6.

A 3 8 r w SPRING AND SHUNT ASSEMBLY FOR CIRCUIT INTERRUPTER BACKGROUND OF THE INVENTION In the construction of circuit interrupters for higher voltage, such as power fuses of the dropout type which include a conducting rod that is movable through an arc-extinguishing means, such as a body of gas evolving material, a problem arises in providing a reliable means for actuating the movement of the conducting rod during arc interruption and a reliable means for actuating the dropout action of the circuit interrupter following are interruption. In certain known interrupter structures of the type described, the movement of the conducting rod is actuated by an associated biasing spring to initiate dropout action of the interrupter, the conducting rod includes an extension which is rigidly mounted on the conducting rod for movement therewith and which is actuated to move through at least a portion of the turns of the associated biasing spring to actuate the dropout action of the interrupter. It has been found in such known interrupter structures, that the movement of the conducting rod which is required for both are interruption and for actuating the dropout action of the overall interrupter may be prevented by the jamming of the extension of the conducting rod with either the turns of the associated biasing spring or with flexible conductors which may be provided as part of a current path extending through the turns of the biasing spring. It has also been found that the turns of the biasing spring in known structures of the type described may tend to overlap during an interruption operataion of the circuit interrupter to prevent proper operation of the interrupter or to cause damage to the turns of the spring to thereby prevent repetitive operations with the same biasing spring. It has been proposed that the use of a helical spring where the spring material has a square cross-section is useful in preventing the aforementioned damage to the turns of the spring. However, the square cross-sectioned material is expensive and difficult to form into a spring. It is therefore desirable to provide an improved circuit interrupter of the type described which includes a more reliable means for both actuating the movement of a conducting rod during an interrupting operation and to actuate the dropout action of the overall interrupter following are interruption. It is also desirable to provide an improved circuit interrupter construction of the type described which may be either of the dropout or non-dropout type in which overlapping of the turns of the biasing spring along with the consequent damage to the spring is prevented during an interrupting operation.

SUMMARY OF THE INVENTION In order to actuate the movement of the elongated conducting member, a helically coiled tension spring is connected between one end of the elongated conducting member and a movable spring seat which is slidably mounted on a relatively stationary conducting member at one end of the casing and which is coupled to a separate tripping rod mounted inside of a tubular portion of the stationary conducting member. When the fusible means blows or fuses, the spring collapses at least partially to actuate the elongated conducting member during arc interruption and collapses fully to actuate the movable spring seat and the tripping rod to thereby actuate dropout movement of the interrupter. Another feature of the invention relates to a circuit interrupter construction of the dropout or non-dropout type including a spring which is disposed within a hollow cylindrical tube so that the spring may not be moved appreciably off of its axis during longitudinal movement thereof. This construction prevents overlapping of the spring turns and damage to the spring during an interrupting operation. The tube is also provided with a set of very long longitudinal oppositely disposed notches in the side wall through which a key may track. This allows the spring to perform properly in a fusing opera tion. However, angularly displaced from the long notches are two spaced oppositely disposed relatively short notches in the side wall of the tube into which the previously described keys can be inserted when the spring has been tensed. This allows for the installation of the renewable fuse unit into the spring and shunt assembly unit and then easy disposition into the circuit interrupter. After it has been disposed in the circuit interrupter, the end of the renewable fuse unit opposite the spring is pulled back to tension the spring and to disengage the keys from the relatively short slots or grooves and then portions of the spring mechanism are rotated until the keys align with the elongated grooves whereupon the spring can adapt its natural tension position in the fuse prior to a fusing operation.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the preferred embodiments exemplary of the invention shown in the accompanying drawings, in which:

FIG. 1 is a side elevation view of a high voltage power fuse structure which is shown in the normally closed position and which may utilize the spring and shunt assembly which embodies the principles of the present invention;

FIG. 2 is a side elevation view partially broken away of a portion of the spring and shunt assembly described in this invention without the spring guide tube;

FIG. 3 is a side elevation view of the spring and shunt assembly of this invention including the spring guide tube;

FIG. 4 is a bottom view of the shunt and spring guide assembly with the outer tube shown in FIG. 3;

FIG. 5 is a partially broken away side elevation similar to FIG. 2 for a shunt and spring guide assembly for a non-dropout type fuse; and

FIG. 6 is a side sectioned view partially broken away of the fuse structure shown in FIG. 1 with spring and shunt assembly of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and FIG. 1 in particular, the structure shown comprises a power fuse structure of the high voltage dropout type, the general arrangement of which is set forth more fully in copending application US. Pat. No. 3,447,] 14 by R. E. Frink and C. T. Walker which is assigned to the same assignee as the present application.

As illustrated in FIG. 1, the fuse structure 10 includes a base (not shown) formed of sheet metal and a pair of outwardly extending insulator supports 272 and 282. The upper insulator support 272 fixedly supports in position a latching assembly 250 which includes a break contact 252, as described in greater detail in the copending application just mentioned. A lower insulator support 282 supports a hinge assembly 260 which pivotally supports a fuse unit 100 and which includes a hinge contact 262 which is mounted in a relatively stationary position on the lower insulator support 282 as described in the copending application just mentioned. As illustrated in FIG. 1, the fuse unit 100 serves to electrically bridge the break contact 252 and the hinge contact 262 so that electric current will normally pass therebetween by way of terminal pads (not shown) to which an external electrical circuit may be connected.

The fuse unit 100 includes a generally tubular fuse holder 32 which is formed from a suitable weatherproof, electrically insulating material, such as a filament wound glass epoxy material or the like, and a pair of upper and lower end fittings or terminals 34 and 36, respectively, which are disposed at the opposite ends of the holder 32 and which are formed from an electrically conducting material. The upper and lower end fittings or terminals 34 and 36, respectively, are securely fastened to the opposite ends of the associated holder or tube 32 by suitable means, such as cement and a plurality of pins which may pass transversely through both the end fittings 34 and 36 and the associated holder 32. As illustrated, the fuse unit 100 also includes a hookeye 274 which is pivotally mounted on a laterally projecting portion 34A on the upper end fitting 34 and which may be utilized for effecting opening and closing movements of the fuse unit 100 by means of a conventional hook-stick. The lower end fitting 36 includes a hinge lifting eye 284 which may be formed integrally with the lower end fitting 36 and which may be employed in conjunction with a conventional hook-stick to effect physical removal of the fuse unit 100 from the hinge assembly 260 for replacement of the fuse unit 100.

Referring now to FIG. 2, the internal portion of a spring and shunt assembly 30' which may be utilized in the fuse structure is shown. The spring and shunt assembly 30' comprises a circular helical spring 76'. The metallic stock for the spring 76' has a circular crosssection as indicated at 76A'. The spring is disposed at its upper end on a spring holder member 74'. The spring holder member 74' has an extension which terminates at a tip 52'. The extension and tip 52' are adapted to extend through an annular opening (not shown) in a conducting member 60'. The conducting member 60' has a threaded upper portion 60C and an integrally attached flanged portion 54'. Disposed on either side of the upper portion of the member 60' are oppositely disposed pin members 58 which extend into the annular opening (not shown) through which the extension and member 52' extends. Member 52' has a shoulder portion 74D thereon which may abut against the inner edges of the pins 58' as the member 52' is moved vertically downward through the annular openings in member 60. This acts as a vertical downward stop for the movement of the pin 52. There is a similar upwardly disposed shoulder (not shown) for abutting against the lower portion of the inward edges of the pins 58' as the member 52' is moved in the upward vertical direction. This latter shoulder provides an upward vertical stop for the pin 52'. The bottom portion of the spring 76' is disposed on a movable terminal member 84B. The movable terminal member 848' has two oppositely disposed keys or protrusions 84, the use of which will be discussed hereafter. Member 84B has a central internally tapped opening 84A' into which a correspondingly threaded member may be inserted and firmly secured. Disposed between the members 74' and 84B is a flexible, electrically conducting conductor member 82'. Conductor member 82' is significantly more electrically conductive than spring member 76' and thus the major portion of electrical current which may flow between terminal and movable terminal 848' flows through the conductive member 82' rather than the spring member 76'. Consequently, shunt member 82' carries most of the current load flowing through the member 30' during either normal or fusing operations. As a result of this, the spring member 76' need not be chosen to accommodate large amounts of electrical current but may be chosen for its mechanical spring properties. Electrically conducting flexible shunt member 82' comprises fastening or securing means 82A at the upper end thereof. The shunt member 82' is brazed and/or riveted to the spring holder member 74 and the movable terminal member 84B. Spring holder member 74' may move vertically downwardly away from the flange member 54' from the place 82E. The amount of downward movement is determined by the length of travel of the pin 52' before the upper shoulder 74D abuts against the upper portion of the innermost parts of the pins 58.

Referring now to FIG. 3, a portion of the spring and shunt guide assembly 30' is shown assembled within a hollow cylindrical tubular member 400. Tubular member 400 has a pair of diametrically oppositely disposed elongated circumferential axial slots 402 adapted to receive and guide the previously described key members 848' during spring compression and tension. Only one of the slots 402 is shown in FIG. 3. Angularly circumferentially spaced from slots 402 is a second set of relatively shorter diametrically oppositely disposed axially oriented circumferential slots 404, only one of which is shown in FIG. 3. Slots 404 are also adapted to accommodate or receive the key members 84B. Terminal member 84' may be moved downwardly towards the bottom of the tube 30' thus causing the integral key portions 843' to move downwardly and out of the slots 402. In this disposition, the spring is highly tense. At this point, the terminal 848' may be rotated angularly or to the left as shown in FIG. 3 to align the key members 848' with the relatively shorter slots 404. The reason for this combination of construction features will be described with respect to FIG. 6. Tube 400 is rigidly attached to flange member 54' as shown in FIG. 3. The attachment may be known as a magneform attachment. Terminal member 60' is shown protruding from the top of the assembly 30. Also shown is a threaded portion 60' of the conducting member 60' and one of the oppositely disposed pins 58'.

Referring now to FIG. 4, a bottom view of the tube assembly 30' of FIG. 3 is shown. The tube member 400 is shown to be tubular, hollow and cylindrical. In a preferred embodiment of the invention, the tube member 400 comprises an aluminum alloy or composition mate rial. Movable terminal member 84 is shown from the bottom. In addition, the two oppositely disposed key members 84B are also shown. The central part of the member 84 is hollow circular and has an internally threaded or topped portion 84A for receiving a threaded member as will be described with respect to FIG. 6. The coiled spring is not shown for convenience of illustration. In addition, the electrically conducting shunt assembly 82' as shown in FIG. 2 is also not shown for convenience of illustration. The rivets 82D are shown. Member 84' comprises two laminated or layed sections riveted together. The oppositely disposed relatively long axially oriented circumferential slots 404 are shown from the bottom in FIG. 4. Displaced from these slots circumferentially by an angle theta (0) are the relatively shorter axially disposed circumferential slots 402. The keys 84B are shown disposed in the relatively short slots 402 in the embodiment of the invention shown in FIG. 4. By pulling the terminal member 84B in a direction which would correspond to a direc tion out from the plane of FIG. 4 and rotating it counterclocltwise by an angle theta (6), the keys may be aligned with the relatively long longitudinal slots 404 whereupon the potential energy of the tensed spring may be released to cause the spring to collapse to a more relaxed position.

Referring now to FIG. 5, another embodiment of the invention comprising member 30" is shown. In this embodiment of the invention which is utilized for a nonknockout or kickout type circuit interrupter, there is no pin member 52 as is shown in FIG. 2. However, member 60 with threaded portion 60C" and pins 58 as well as flange member 54' may be the same as in the embodiment of the invention of FIG. 2. In addition, the spring member 76", the attachment member 82A" and the shunt conducting assembly 82" are also the same as is shown in FIG. 2. In addition, the shunt conductor material 82" is brazed or otherwise conveniently attached and secured to the spring holder member 74". In this embodiment of the invention, however, there is no provision for downward movement of the member 74" relative to the flange 54". Said in another way, there will be no opening or gap created at the place 82E of FIG. 5.

Referring now to FIG. 6, an embodiment of the invention utilizing the shunt and spring assembly as shown in FIGS. 2 and 3 is shown. The fuse unit 100 includes a removable or refillable unit which is mounted within the holder structure which includes the outer tube 32 and the upper and lower end fittings or terminals 34 and 36 respectively. The removable unit 20 includes its own supporting tube or insulating casing 108 which is formed from a suitable electrically insulating material having sufficient strength to withstand the internal gas pressures and intense heat which result during an interrupting operation of the fuse unit 100, such as a filament wound glass epoxy material. A body of gas evolving material, such as boric acid, which may include a plurality of generally annular blocks 122, 124, 126 and 128 are disposed inside the tube 108 and spaced from the ends thereof. Each of the blocks I22, I24, I26 and 128 include a relatively larger central opening and a relatively smaller opening at one side thereof, booth of which extend axially through the individual blocks. When the blocks 122, 124, 126 and 128 are axially stacked in end-to-end relation, as shown in FIG. 6, with the respective larger and smaller openings thereof substantially aligned, a main bore 130 is formed through the body of gas evolving or arc-extinguishing material which includes said blocks and a relatively small auxiliary bore 192 is formed through the body of gas evolving material.

In order to prevent the travel of ionized gases between the main bore 130 and the auxiliary bore 192 during an interrupting operation of the fuse unit 100 as described in greater detail in U.S. Pat. No. 3,40l,243, which is assigned to the same assignee as the present application, the meeting surfaces of the blocks 122, 124, 126 and 128 are structurally joined to one another around the relatively smaller openings of said blocks which form the auxiliary bore 192 by a sealing and bonding material having a relatively high dielectric strength, such as an epoxy resin. More specifically, as explained in the patent just mentioned, the meeting surfaces of the blocks I22, 124, I26 and 128 each includes a groove or recess which extends substantially around and is spaced from the relatively smaller opening in each of said blocks and forms with the corresponding recess in the end of the adjacent blocks a larger passageway which is substantially filled with the sealing and bonding material, as indicated at 132 in FIG. 6. It is to be noted that the manner in which the blocks 122, 124, I26 and 128 are bonded to one another around the auxiliary bore 192 substantially prevents the entrance of the sealing and bonding material employed into either the auxiliary bore 192 or into the main bore 130.

In order to limit the gas pressures which result during an interrupting operation of the fuse unit inside the tube 108 to a value within the rupture strength of the tube 100, as disclosed in greater detail in U.S. Pat. No. 3,401,246, which is assigned to the same assignee as the present application, each of the blocks 126 and 128 includes a generally C-shaped recess, as indicated at 129, in FIG. 6 which extends axially from one end of each of said blocks to a point which is adjacent to and axially spaced from the other end of the respective blocks, with each of the recesses terminating peripherally short of the portion of each of said blocks which includes the relatively smaller openings which form part of the auxiliary bore 192. Each of the blocks 126 and 128 therefore includes around a major portion of its inner periphery a frangible inner wall, as indicated at 126A and 128A, respectively, which is arranged to disintegrate when the fuse unit 100 is called upon to interrupt relatively large currents and when the intense heat results within the main bore 130 and the gas pressure within the main bore 130 exceeds a predetermined value. During such an interrupting operation, the size or cross-section of the main bore 130 through the blocks 126 and 128 is effectively increased by the disintegration of the inner walls 126A and 128A of the blocks 126 and 128, respectively, to thereby increase the size of the gas passageway and decrease or limit the gas pressure which would otherwise result.

In order to retain the blocks 122, 124, 126 and 128 in assembled relationship with the associated tube 108 as shown in FIG. 6, the outer surfaces of said blocks may be coated with a suitable cement or bonding material, such as an epoxy bonding material prior to assembly of the blocks inside the tube 108. In addition, a generally tubular or annular retaining member or plug 189 may be disposed at the upper end of the blocks 122, I24, I26 and 128 with the major portion of the retaining member 189 extending axially inside the tube 108. The retaining membe 189 may be formed or molded from a suitable electrically insulating material having sufficient strength to assist in retaining the blocks 122, I24, I26 and 128 in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, such as a glass polyester material. A washer 183 formed from similar material may be disposed between the retaining member 189 and the uppermost block 122, as shown in FIG. 6, and may be employed during the preassembly and bonding of the blocks 122, 124, 126 and 128 together prior to the assembly of said blocks inside the tube 108. It is to be noted that the retaining member 189, as well as the washer 183, includes a relatively larger central opening which forms an extension of the main bore 130 and a relatively smaller opening which forms an extension of the auxiliary bore 192.

In order to assist in retaining the member 189 in assembled relation with the associated tube 108 during an interrupting operation of the fuse unit 100, the outer surface of the retaining member 189 and the inner surface of the tube 108 at the upper end of the tube 108 include adjacent helical grooves which together from a passageway in which a helical wire 181 is disposed to firmly secure the retaining member 189 in assembled relation with the tube 108. The retaining member 189 may be assembled with the upper end of the tube 108 by first assembling the helical wire 181 in the helical groove around the outer surface of the retaining member 189 and then screwing the retaining member 189 into the upper end of the tube 108 to the final position shown in FIG. 6. It is to be noted that the outer surface of the retaining member 189 may also be coated with a suitable cement or bonding material, such as an epoxy bonding material to additionally secure the retaining member 189 to the tube 108.

In order to substantially prevent the escape of ionized gases from the upper end of the refillable or renewable unit around the elongated conducting member 83 which extends through the main bore 130, a generally tubular member 185 is disposed in concentric or nested relation with the retaining member 189, as shown in FIG. 6, and is preferably formed from an electrically insulating material having a relatively low coefficient of friction, such as polytetrafluoroethylene which is sold under trademark Teflon. A shoulder portion 185A is provided at the upper end of the tubular member 185 and includes a central opening of reduced cross-section or size through which the conducting member passes and which forms a substantially gastight seal with the conducting member 83 during an interrupting operation of the fuse unit 100 when the conducting member 83 is actuated to move axially upwardly, as viewed in FIG. 6. The tubular member 185 also acts as a bearing to guide the axial movement of the conducting member 83. in order to prevent the tubular member 185 from being blown out of the upper end of the tube 108 during an interrupting operation of the fuse unit 100, the retaining member 189 includes an inner shoulder portion against which the upper end of the tubular member 185 bears as shown in FIG. 6. The escape of ionized gases from the upper end of the renewable unit 20 from the auxiliary bore 192 may be adequately prevented by reducing the size of the relatively smaller opening through the retaining member 189 through which the auxiliary conductor 182 passes so that the cross-section of the auxiliary conductor 182 substantially fills the relatively smaller opening through the retaining member 189.

In order to further assist in retaining the blocks 122, l24, 126 and 128 in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, a generally tubular or annular retaining member 142 is disposed inside the tube 108 at the lower end of the blocks 122, 124, 126 and 128, as shown in FIG. 6, and is formed or molded from an electrically insulating material having sufficient strength to assist in retaining the blocks 122, 124, 126 and 128 inside the tube 108 during such an interrupting operation, such as a glass polyester material. The outer surface of the retaining member 142 is preferably coated with a suitable cement or bonding material, such as an epoxy bonding material, prior to the assembly of the retaining member 142 inside the tube 108. This bonding material serves to secure the retaining member 142 to the inside of the tube 108. The retaining member 142 includes a relatively larger opening 142A which extends axially therethrough, into which the lower end of the main bore 130 opens and which may serve as an exhaust passageway for high pressure gases which result during the operation of the fuse unit 100. The opening 142 may also serve as a chamber in which the fusible means 160 is disposed. The retaining member 142 also includes a relatively smaller opening 142B which extends axially therethrough. The lower end of the auxiliary bore 192 opens into the opening 142B and the lower end of the auxiliary conductor 182 projects into the same opening. The insulating wall or partition 142C which is formed integrally with the retaining member 142 around the relatively smaller opening 1423 through the retaining member 142 assists in preventing certain are products which may result during the operation of the fuse unit in the relatively smaller opening 14213 from being deflected into the relatively larger opening 142A of the retaining member 142 and impinging on parts of the fusible means 160. The retaining member 142 also includes an upwardly projecting tubular portion 142D adjacent to the relatively smaller opening 142B through the retaining member 142 with the projecting portion 142D being joined to the adjacent block 128 around a recess in the block 128 which is adapted to receive the projecting portion 142D by a flexible bonding material, such as silicone rubber. This joint between the retaining member 142 and the block 128 around the auxiliary bore 192 assists in preventing the travel or escape of ionized gases between the auxiliary bore 192 and the main bore and between the auxiliary bore 192 and the relatively larger opening 1428 through the retaining member 142 during an interrupting operation of the fuse at 100.

The elongated conducting member or rod 82 of the refillable unit 20 is normally disposed as shown in FIG. 6 to extend through the main bore 130 with the upper end of the conducting rod 83 projecting axially beyond the upper end of the tube 108 and with the upper portion of the conducting rod 83 being externally threaded, as indicated at 83A. The conducting rod 83 is normally held in the position shown in FIG. 6 by a connection through the fusible means 160 to the generally annular or tubular lower conducting member or contact 150.

More specifically, the fusible means 160 comprises a strain element 162 and a fusible element or link 164. The upper end of the strain element 162 is secured by suitable means, such as brazing, to the lower end of the conducting rod 83, while the other end of the strain element 162 is secured by suitable means, such as brazing, to the connecting conductor or terminal 156 which is of the flat strip type. The connecting conductor 156 is secured, in turn, to the lower contact adjacent to the upper end of the lower contact 150 such as brazing.

Similarly, the upper end of the fusible element or link 164 is secured to the lower end of the conducting rod 83 by suitable means, such as brazing, while the lower end of the fusible element or link is secured to the lower contact 150 adjacent to the upper end of the lower contact 150 by'suitable means, such as brazing. It is to be noted that the strain element 162 and the fusible element 164 are electrically connected in parallel between the lower end of the conducting rod 83 and the lower contact 150 of the removable unit 20.

Similarly, the auxiliary conductor 182 which is of a relatively smaller cross-section or size compared with that of the conducting rod 83 normally extends through the auxiliary bore 192 with the upper end of the auxiliary conductor 182 extending axially beyond the upper end of the auxiliary bore 192 and being both mechanically and electrically connected to the upper portion of the conducting rod 83 by a transversely extending spring pin 184. The pin 184 is disposed in a transversely extending recess or opening provided at the upper end of the retaining member 189 to prevent rotation of the conducting rod 83 after assembly of the rod 83 into the renewable unit 20. The upper end of the auxiliary conductor 182 may be formed as a loop which is assembled over the conducting pin 184 and retained thereon by the head 186 of the spring pin 184. The lower end of the auxiliary conductor 182 extends or projects into the relatively smaller opening 1428 of the retaining member 142, as shown in FIG. 6, and is electrically connected through a helical conducting wire of reduced cross-section as indicated at 194 to an angle-shaped auxiliary stationary terminal 157 which is secured to the tubular conducting member or contact 150 adjacent to the upper end of the member 150 by suitable means, such as brazing. The upper end of the helical wire 194 which is disposed inside the relatively smaller opening 142B is secured to the lower end of the auxiliary conductor 182 by suitable means, such as brazing, and the lower end of the helical wire 194 is secured to the auxiliary terminal 157 by suitable means, such as crimping or brazing, as disclosed in greater detail in U.S. Pat. No. 3,401,247, which is assigned to the same assignee as the present application.

The lower contact or conducting member 150 also includes an elongated arcing terminal 158 as disclosed in the patent just mentioned which projects upwardly from the upper end of the contact 150 into the relatively smaller opening 142B of the retaining member 142 to axially overlap the lower end of the auxiliary conducting member 182 with the lower portion of the arcing terminal 158 being disposed adjacent to and generally parallel to the axis of the helical wire 194. The arcing terminal 158 is electrically insulated along its length by a coating or film of electrically insulating material, such as an insulating enamel, which is provided on the arcing terminals 158 to prevent the electrical shorting out of the helical wire 194. The arcing terminal 158 which is formed from an electrically conducting material may be structurally secured to the upper end of the lower contact 150 at the inner periphery thereof by suitable means, such as brazing, or may be formed integrally therewith in a particular application. It is to be noted that the auxiliary current path which extends from the upper portion of the conducting rod 83, through the cross pin 184, the auxiliary conductor 182 and the helical wire 194 to the auxiliary terminal 157 on the lower contact 150 is also electrically connected in parallel with the conducting paths which include, respectively, the strain element 162 and the fusible element 164.

In order to assist in retaining the blocks 122, 124, 126 and 128 and the retaining member 142 in assembled relationship outside the tube 108, as well as for another important purpose, during an interrupting operation of the fuse unit 100, the lower tubular conducting member or contact includes a main portion 152 which extends axially inwardly from the lower end of the tube 108 to bear against the lower end of the retaining member 142. The lower contact 150 also includes a flange portion 154 at the lower end thereof against which the lower end of the tube 108 bears when the conducting member 150 is assembled with the fuse tube 108.

In order to retain the lower contact 150, as well as other parts of the renewable unit 20, in assembled relationship with the tube 108 during an interrupting operation of the fuse unit 100, a generally tubular external terminal member or ferrule 172 is disposed to telescope or extend axially over the lower end of the tube 108. In order to firmly secure the external terminal member 172 to the lower end of the tube 108, the internal surface of the external terminal member 172 and the external surface of the portion of the tube 108 ad jacent to the member 172 include adjacent helical grooves which, when the parts are assembled, form a helical passageway in which a helical wire 173 is disposed. In the assembly of the external terminal member 172 on the lower end of the tube 108, the helical wire 173 may be first assembled in the helical groove on the lower end of the tube 108 and the external terminal member 172 may then be screwed onto the lower end of the tube until the parts reach their final positions as shown in FIG. 6. In order to additionally assist in retaining the external terminal member 172 on the lower end of the tube 108, the outer surface of the tube 108 and the inner surface of the external terminal member 172 may be coated with a cement or bonding material, such as an epoxy bonding material, prior to the assembly of the external terminal member 172 on the lower end of the tube 108. It should be noted that the external terminal member 172 also includes an inwardly projecting flange portion 172A around a central opening in member 172 which bears against the adjacent flange portion 154 of the tubular conducting member 150 to assist in retaining the tubular conducting member 150 in assembled relation with the other parts of the renewable unit 20.

In order to form a current conducting path which extends between the lower end fitting 36 and the lower contact 150 of the renewable unit 20, the external terminal member 172 also includes an external flange portion 172C which bears against the inwardly projecting flange portion 36B at the shoulder 36C of the lower end fitting 36. The electrically conducting path thus formed extends to the lower contact 150 through the inwardly projecting flange portion 172A of the external terminal 172 and through the externally projecting flange portion 172C to the inwardly projecting flange portion 36B of the lower end fitting 36. The area of current transfer path between the external terminal 172 of the removable unit 20 and the lower end fitting 36 may also be augmented by the contact ring which may be formed of electrically conducting material and which is disposed to threadedly engage the internally threaded opening provided at the lower end of the end fitting 36 and to bear against the external terminal member 172 of the renewable unit as shown in FIG. 6.

It is important to note that in order to prevent the concentration of relatively high potential stresses adjacent to the external terminal member 172 during an interrupting operation of the fuse 100 at relatively high voltages, the upper end of the lower contact 150 extends axially beyond the upper end of the external terminal member 172 toward the other end of the tube 108 a minimum distance to prevent such a concentration of relatively high potential stresses externally of the tube 108 adjacent to the external terminal member 172 as disclosed in greater detail in US. Pat. No. 3,401,245, which is assigned to the same assignee as the present application.

In order to actuate the movement of the conducting rod 83 as well as that of the auxiliary conductor 182, during an interrupting operation of fusion at 100 and to electrically connect the renewable or refillable unit 20 described to the upper end fitting of terminal 34, the spring and cable assemblies including the outer tube 400 is disposed inside the outer holder or tube 32 between the renewable unit 20 and the upper end fitting 34. The spring and cable assembly 30' includes at its lower end the previously described conducting member 84' having an internally threaded central opening as indicated at 84A to receive the upper threaded end 83A of the conducting rod 83. A lower spring seat member or movable terminal 86' includes provisions for accepting the helically threaded spring 76' in appropriate grooves in the edges of the member 86. The spring and cable assembly 30 also includes the generally planar upper spring assembly 74' which includes a grooved outer portion and which contains the upper extended portion 52' which is slidably disposed in an annular opening 72 of the generally cylindrical conducting member 60' As is shown in FIG. 6, the lower or flange portion 54 of the conducting member 60' projects inside the upper end of the outer holder 32. The integral upper portion of the conducting member 60' extends axially through an annular opening 348 in the upper end fitting 34 and is externally threaded at the upper end thereof as indicated at 60C As illustrated, the generally cylindrical conducting member 60 may be secured to the upper end fitting 34 by an internally threaded end cap 44 which may be screwed down on the upper thread portion 60C of the conducting member 60 until the flange portion 44A of the end cap 44 bears against the upper end fitting 34 around a flange or shoulder portion as indicated at 34C in FIG. 6.

In order to actuate the release of the latching assembly 250 shown in FIG. 1 following an interrupting operation by the fuse unit 100, a tripping rod or member having a generally cylindrical, elongated shape is slidably disposed inside a central opening or passageway 72' which is internally threaded at its upper end and which extends axially from a point which is axially spaced from the lower end of a conducting member 60 to the other end of the conducting member 60' as shown in FIG. 6. The upper end of the tripping rod 52' is normally positioned below the top of the end cap 44, as shown in FIG. 6. The lower end of the tripping rod 52' is fixedly coupled to or integral with the upper spring seat 74' for corresponding axial movement therewith. In order to permit the axial movement of the tripping rod 52' upwardly through the end cap 44 following an interrupting operation of the fuse unit 100, the top of the end cap 44 includes a central opening 46 through which the tripping rod may pass to actuate the release of the latching assembly 250 shown in FIG. 1. When the latching assembly 250 is released by the tripping rod 52, the upper end of the fuse unit will be actuated to rotate in a clockwise direction, as viewed in FIG. 1, about the lower hinge assembly 260 to thereby provide an electrically insulating gap between the upper break contact.

In order to assemble the renewable unit 20 and the associated spring and cable assembly 30 into the holder 32, the threaded end of the conducting rod 83 is first screwed into the socket 84A at the lower end of the spring and cable assembly 30'. A refill fusing tool (not shown) is then screwed into the internally threaded central opening or passageway 72 at the other end of the spring and cable assembly 30'. The flange member 20' is then drawn back such as by pulling against member 172C as shown in FIG. 6 until the spring is fully tensed and the keys 84B are then inserted into the relatively short grooves or openings 402 in the side wall of the tube 400 in a manner described with respect to FIGS. 3 and 4. The spring and cable assembly 30' is then inserted into the outer holder 32 with the upper end of the spring and cable assembly 30' being inserted first into the lower end of the outer holder 32' as viewed in FIG. 6 until the refill fusing tool (not shown) passes through the central opening 343 of the upper end fitting 34. The cross pins 58' mounted at the sides of the upper portion of the conducting member 60' are pushed upwardly through a pair of radial slots (not shown) provided in the upper end fitting 34 around the central opening 34B by forcing against the bottom part of the flange 172C. The upper conducting members 60' and the spring and cable assembly 30' are then rotated by rotating flange 172C which is projecting at this time from the bottom of the terminal 36 until the pin 58 rests on the shoulder provided at the bottom of the enlarged opening 34E in the upper end fitting 34. The end cap 44 may be then screwed down on the upper threaded portions 60C of the conducting member 60 to further stretch the spring 66 to a final charge condition or position shown in FIG. 6 with the cross pins 58 drawn upwardly away from the shoulder in the upper end pin 34 at the bottom of the enlarged opening 34E. It is to be noted at this point the flange 172C is pulled vertically downwardly to further tense the spring 82 and to remove the keys 84B from the relatively small grooves 84B as shown in FIGS. 3 and 4. The flange and the entire refill assembly 20 as well as the member 84' is rotated by theta (6) degrees until the keys 84B align with the keyways or slotted openings 404 whereupon the flange member is set free and allowed to be pulled upwardly to contract the spring member 76 and cause the flange member 172C to seat in a proper manner within the fuse holder 36. It should be noted that when the spring 76' is being moved downwardly, the pin 52 is caused to move vertically downwardly from the shoulder position 74C which would abut against the inner portions of the pins 58' until the upper shoulder portion 74D abuts against the upper sides of the inner portions of the pins 58. While this free movement is occurring, the spring is not actually being tensed but is rather translated vertically downwardly in a manner which does not cause any change in the tension of the spring. However, once the shoulder 74D abuts against the upper sides of the pins 58' further downward movement of the members 84' will cause a tensing of the spring 76'. Likewise, when the spring is relaxed, little or not upward movement of the pin 52 occurs until the spring has been completely relaxed. In a fusing operation, the member 83 would be drawn upwardly through the opening 130 in a vertical direction by the relaxing spring 76'. When the spring has fully relaxed, the inertia of the moving member 83' will then cause the pin 52' to move upwardly until the shoulder 74C abuts against the lower side of the pin 58 and the pin 52' thus protrudes out of the hole 46. This will cause a triggering of the dropout action as was described previously.

In considering the operation of the fuse unit 100, it is to be noted first that the current paths which include, respectively, the strain element 162, the fusible element 164, and the helical wire 194, which is connected in series with the auxiliary conductor 182, are all electrically connected in parallel between the upper end of the conducting rod 83 and the lower contact 150 at the lower end of the renewable unit 20. The resistance of the current path which includes the fusible element 164 and which is calibrated to have predetermined timecurrent characteristics is arranged to be relatively much less than the resistance of either the path which includes the strain element 162 or the path which includes the helical wire 194 so that normally most of the current which flows through the fuse unit 100 is carried by the fusible element 164. Although the resistance of the current path which includes the strain element 162 is relatively greater than that of the path which includes the fusible element 164, the resistance of the path which includes the strain element 162 is relatively less than that of the path which includes the helical wire 194 so that when the fusible element 164 melts or blows, most of the current which was formerly carried by the fusible element 164 is then transferred to the strain element 162. In other words, when the current which is flowing through the fuse unit 100 increases to a value which is of sufficient magnitude and duration to melt or blow the fuse element 164, most of the current of which is flowing through the fuse unit 100 then transfers to the strain element 162. When the current which is transferred to the strain element 162 after the melting of the fusible element 164, is sufficient to melt or blow the strain element 162, the current which was previously carried by the strain element 162 is finally transferred to the current path through the auxiliary bore 192 which includes the auxiliary conductor 183 and the helical wire 194. When the strain element 162 melts or blows, the conducting rod 83 is no longer restrained from upward movement under the influence of the biasing spring 76' and the conducting rod 83 and the auxiliary conductor 182 will start to move upwardly under the influence of the spring 76' to thereby stretch the helical wire 194 which is electrically connected to the bottom of the auxiliary conductor 182. It is to be noted that the stretching of the helical wire 194 permits limited travel of both the conducting rod 83 and the auxiliary conductor 182 while maintaining a continuous electric circuit or path through the auxiliary bore 192 and that as long as the current path which includes the auxiliary conductor 182 and the helical conductor 194 is intact, no arcing will take place in either the main bore 130 or an auxiliary bore 192. In other words, stretching of the helical wire 194 during the initial movement of the conducting rod 83 and the auxiliary conductor 182 following the melting or blowing of the fusible element 164 and the strain element 162 will permit the formation of an electrically insulating gap in the main bore 130 while initially delaying the formation of a significant insulating gap in the auxiliary bore 192.

After the strain element 162 melts or blows as just described, and the conducting rod 83 and the auxiliary conductor 182 begin to move upwardly to thereby stretch the helical wire 194, the helical wire 194 will either fracture mechanically when stretched to its limit or the current transferred to the current path which includes the helical wire 194 and the auxiliary conductor 182 will be sufficient to melt or blow the helical wire 194 which is of reduced cross-section compared to that of the auxiliary conductor or rod 182. After the helical wire 194 is melted or otherwise broken, an arc will be initiated between the retreating end of either the broken helical wire 194 or the auxiliary conductor 182 and the terminal 157 or the arcing terminal 158, which axially overlaps the lower end of the auxiliary conductor 182, to thereby burn through the electrical insulation on the arcing terminal 158. Even after the wire 194 melts or is broken, the formation of a significant electrically insulating gap in the auxiliary bore 192 is further delayed by the overlapping of the auxiliary conductor 182 by the arcing terminal 158 until the retreating free end of either the wire 194 or the conductor 182 passes the upper end of the arcing terminal 158 whose insulation will have burned through by this time. It is important to note that the insulating gap in the main bore 130 between the separated ends of the conducting parts will increase at a faster rate than the formation of an insulating gap in the auxiliary bore 192 due to both the delay in the formation of an arc in the auxiliary bore 192 because of the presence of the helical wire 194 and due to the overlapping of the auxiliary conductor 182 by the arcing terminal 158. It is also important to note that the arcing which takes place in the fuse unit during an interrupting operation will always take place initially in the auxiliary bore 192 as just explained. When the retreating end of either the helical wire 194 or the auxiliary conductor 182 passes the upper end of the arcing terminal 158, the arcing which takes place initially in the auxiliary bore 192 will cause gases to be evolved from the gas evolving material around the auxiliary bore 192 which will be un-ionized. When the current to be interrupted by the fuse unit 100 is relatively low, such as l,000 amperes or less, and when the gas pressure of the evolved gases in the auxiliary bore 192 increases to thereby increase the corresponding dielectric strength in the auxiliary bore 192, the insulating gap which is formed in the auxiliary bore 192 along with the corresponding increased dielectric strength, will be sufficient to interrupt the alternating current being interrupted following a particularly current zero in the auxiliary bore 192. The insulating gap which is formed simultaneously in the main bore of the fuse unit 100 at a relatively faster rate will have sufficient dielectric strength considering the instantaneous potential difference between the separating conducting parts in the main bore 130 of the fuse unit 100 to prevent a restrike of the arc in the main bore 130 for such relatively low fault currents. In other words, when any fault current is interrupted by the fuse unit 100, as

just described, arcing will always be initiated in the auxiliary bore 192 and for relatively smaller fault currents, the arcing which results will be finally interrupted in the auxiliary bore 192. One important reason for this is that the dielectric strength of the main bore 130 at the time that the arc is finally interrupted in the auxiliary bore 192 will be relatively higher than that in the auxiliary bore 192 to prevent a restrike or breakdown of the main bore 130 due to the instantaneous potential difference which exists or results between the separated conducting parts in the main bore 130 at the time of arc interruption in the auxiliary bore 192.

For relatively higher fault currents, the arcing which is initiated in the fuse unit 100 will still be initiated in the auxiliary bore 192 in the manner just described. For such relatively higher current faults, however, the gas pressure which builds up in the auxiliary bore 192 dur ing an interrupting operation and the burning back of the separating conducting parts in the auxiliary bore 192 will result in a relatively higher dielectric strength in the auxiliary bore 192 compared with that in the main bore 130 between the separated conducting parts in the main bore 130. If the instantaneous potential difference between the separate ends of the conducting parts in the main bore 130 is sufficient when the dielectric strength of the main bore 130 becomes relatively less than that of the auxiliary bore 192, the arc will restrike in the main bore 130 to thereby cause the evolution of un-ionized gases in the main bore 130 to thereby increase the gas pressure in the main bore 130, as well as the corresponding dielectric strength in the main bore 130. The are which restrikes the main bore 130 will be elongated both by the upward movement of the conducting rod 83 and by the burning back of the separated conducting parts in the main bore 130 to thereby increase the quantity of un-ionized gases evolved from the gas evolving material disposed around the main bore 130. The are in the main bore 130 will be finally interrupted following a particular current zero in the alternating current which is being interrupted when the insulating gap and the corresponding dielectric strength in the main bore 130 is sufficient to withstand the instantaneous potential difference between the separated conducting parts in the main bore 130. If the fault current which is being interrupted is of a relatively still higher magnitude, the gas pressure in the main bore 130 along with the intense heat which results may be sufficient to disintegrate the inner walls of the blocks 126 and 128 to thereby limit the gas pressure of the evolved gases to a value within the rupture strength of the tube 108 as previously explained. It is to be noted that when the arc is interrupted in the main bore 130 as just described to thereby cause the evolution of gas from the gas evolving material in the blocks 122, 124, I26 and 128 which surround the main bore 130, the upward movement of the conducting rod 130 along with the upward movement of the auxiliary conductor 182 will be additionally accelerated by the force of the gas pressure of such evolved gases in the main bore 130 along with the force exerted on the conducting rod 83 by the biasing force of the spring 76.

During an interrupting operation of the fuse unit 100 as just described, when the conducting rod 83 is released and moved upwardly under the influence of the spring 76 or under the influence of both the spring 76' and the gas pressure of the evolved gases inside the renewable unit 20, the turns of the spring 76' which are normally held in tension will tend to collapse toward a fully compressed condition but after the turns of the spring 76' at least partially collapse, the upper spring seat 74' will begin to slide axially until the upper end of the spring seat 74' impacts or bears against the washer or flange 54' and the turns of the spring 76 reach a fully compressed or fully collapsed condition. During the initial partial collapse of the spring 76, the conducting rod 83 and the auxiliary conductor 182 will be actuated upwardly to finally interrupt the are which is formed either in the main bore I30 or in the auxiliary bore 192, as previously described. During the final collapse of the turns of the spring 76' the axial movement of the upper spring seat 74' will continue until the upper end of the spring seat 74' impacts against the washer or flange 54'. The tripping rod 52' will be actuated from the position shown in FIG. 6 until the upper end of the tripping rod 52 projects axially beyond the upper end of the end cap 44 to actuate the release of the latching means 250, as described in the U.S. Pat. No. 2,403,12l which issued July 2, 1946 to H. L. Rawlins et al.

It is to be noted that the spring 76' may be employed according to one embodiment in a sequential operation to first actuate the movement of the conducting rod 83 and the auxiliary conductor 182 which is required to accomplish arc interruption either in the main her or in the auxiliary bore 192 and then after arc interruption is accomplished to actuate the tripping rod 52' to thereby actuate the release of the latching means 250 and the dropout action of the fuse structure 10. It is also to be noted that the upward movement of the conducting rod 83 and the auxiliary conductor 182 will establish the electrically insulating gaps previously described between the separated ends of the conducting parts inside the renewable unit 20 during an interrupting operation. In addition, the fuse unit 100 will be actuated by the release of the latching means 250 by the tripping rod 52' to rotate in a clockwise direction about the lower hinge assembly 260 in a dropout movement to establish a larger electrically insulating gap between the break contact 252 and the lower stationary hinge contact 262 of the fuse structure 10.

It is to be understood that the teachings of the applicants invention may be applied to power fuses for high voltage application which do not include a tabular conducting member or shield such as the lower contact shown in FIG. 6 but which employs a lower contact ring of the type disclosed in U.S. Pat. No. 3,401,247 previously mentioned.

The apparatus embodying the teachings of this invention have several advantages. For example, in the applicants construction the fuse renewable unit may be assembled on the shunt and spring guide assembly prior to inserting the combination thereof into the fuse holder 32. This is significantly more convenient that the previous method for installing renewable units in the fuses of the type shown. Another advantage lies in the fact that a simple spring having stock of a circular cross-section may be used without significant overlapping of the turns during a compressing action thereof, as may otherwise occur immediately after a fusing action has begun to take place, because of the presence of the guide tube which prevents the turns from overlapping because no significant radial, transverse or outward freedom of movement is allowed.

What is claimed is:

l. A high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material disposed inside of and spaced from the ends of the holder and including at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the conducting member and one of the terminal means, a first conducting member secured to the other terminal means and having a main portion projecting axially into the holder, a spring holder member slidably disposed on the main portion of the first conducting member, a spring connected between the other end of the elongated conducting member and said spring holder member, a flexible helically coiled conductor connected between the main portion of the first conducting member and the other end of the elongated conducting member, and means movably mounted on the first conducting member and coupled to the spring holder member to be actuated by said spring when the fusible means blows for projecting axially beyond the other terminal means, an elongated tubular spring guide attached at one end thereof to said main portion of said first conducting member, said spring being disposed axially within said elongated tubular spring guide, said elongated tubular spring guide cooperating with said spring to prevent said spring from fouling when said fusible means blows.

2. The combination as claimed in claim 1 wherein the spring comprises a plurality of helically coiled turns and the coiled conductor is disposed inside the turns of the spring.

3. The combination as claimed in claim 1 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.

4. The combination as claimed in claim 2 wherein said elongated tubular insulating holder has an elongated axial Opening therein, and a spaced short'axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.

5. The combination as claimed in claim 1 wherein a pair of vertically spaced, relatively stationary contacts is provided, means is provided for pivotally supporting the holder adjacent one end near the lower of the contacts to permit movement of said other terminal means into and out of engagement with the other contact, and a latch means is disposed adjacent to the other contact for releasably maintaining the holder in a closed circuit position with both of said contacts until actuated by said tripping rod to release the holder.

6. The combination as claimed in claim 5 wherein the spring comprises a plurality of helically coiled turns and the coiled conductor is disposed inside the turns of the spring.

7. The combination as claimed in claim 5 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.

8. The combination as claimed in claim 6 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.

9. A high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material inside of and spaced from the ends of the holder and including at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the elongated conducting member and one end of the terminal means, a helically coiled spring connected between the other end of the elongated conducting member and the other terminal means to actuate the movement of the elongated conducting member away from said one of the terminal means upon the fusion of the fusible means, an elongated tubular spring guide attached at one end thereof to said other terminal means, said spring being disposed axially, within said elongated tubular spring guide, said elongated tubular spring guide cooperating with said spring to prevent said spring from fouling when said elongated conducting member is actuated to said movement.

10. The combination as claimed in claim 9 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter upon the fusion of said fusible means. 

1. A high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material disposed inside of and spaced from the ends of the holder and including at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the conducting member and one of the terminal means, a first conducting member secured to the other terminal means and having a main portion projecting axially into the holder, a spring holder member slidably disposed on the main portion of the first conducting member, a spring connected between the other end of the elongated conducting member and said spring holder member, a flexible helically coiled conductor connected between the main portion of the first conducting member and the other end of the elongated conducting member, and means movably mounted on the first conducting member and coupled to the spring holder member to be actuated by said spring when the fusible means blows for projecting axially beyond the other terminal means, an elongated tubular spring guide attached at one end thereof to said main portion of said first conducting member, said spring being disposed axially within said elongated tubular spring guide, said elongated tubular spring guide cooperating with said spring to prevent said spring from fouling when said fusible means blows.
 2. The combination as claimed in claim 1 wherein the spring comprises a plurality of helically coiled turns and The coiled conductor is disposed inside the turns of the spring.
 3. The combination as claimed in claim 1 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.
 4. The combination as claimed in claim 2 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.
 5. The combination as claimed in claim 1 wherein a pair of vertically spaced, relatively stationary contacts is provided, means is provided for pivotally supporting the holder adjacent one end near the lower of the contacts to permit movement of said other terminal means into and out of engagement with the other contact, and a latch means is disposed adjacent to the other contact for releasably maintaining the holder in a closed circuit position with both of said contacts until actuated by said tripping rod to release the holder.
 6. The combination as claimed in claim 5 wherein the spring comprises a plurality of helically coiled turns and the coiled conductor is disposed inside the turns of the spring.
 7. The combination as claimed in claim 5 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.
 8. The combination as claimed in claim 6 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter when said fuse blows.
 9. A high voltage circuit interrupter comprising a tubular insulating holder, a body of arc extinguishing material inside of and spaced from the ends of the holder and including at least one passageway extending axially therethrough, terminal means disposed adjacent to each end of the holder, an elongated conducting member disposed to extend axially through said passageway, fusible means disposed inside the holder and connected between one end of the elongated conducting member and one end of the terminal means, a helically coiled spring connected between the other end of the elongated conducting member and the other terminal means to actuate the movement of the elongated conducting member away from said one of the terminal means upon the fusion of the fusible means, an elongated tubular spring guide attached at one end thereof to said other terminal means, said spring being disposed axially, within said elongated tubular spring guide, said elongated tubular spring guide cooPerating with said spring to prevent said spring from fouling when said elongated conducting member is actuated to said movement.
 10. The combination as claimed in claim 9 wherein said elongated tubular insulating holder has an elongated axial opening therein, and a spaced short axial opening therein, a key portion disposed where said spring is connected to said elongated conductor, said key being disposed in said short axial opening during the time of assembly of said spring and said elongated conductor in said circuit interrupter, and said key being disposed in said elongated axial opening thereafter for allowing spring movement relative to said circuit interrupter upon the fusion of said fusible means. 